The present invention relates to an apparatus for causing thermal coagulation and, more particularly, relates to an apparatus for applying intense light radiation to a limited area of tissue for causing thermal coagulation that results in tissue necrosis.
Various medical procedures require an apparatus to cause hemorrhoid shrinkage or cause coagulation at a site of bleeding. For example, coagulation may be induced at the site of a bleeding hemorrhoid or at a site of hemorrhaging at a bleeding blood vessel stump. Known coagulation systems, for example, use high frequency electric currents to cause coagulation. These systems, however, use the human body as an electrical conductor and thus require external grounding using a grounding pad. Further, such electrosurgical devices do not readily induce coagulation in a controllable and reproducible manner, and thus the depth of necrosis cannot be precisely controlled. Additionally, the metallic probes used tend to adhere to the tissue, thereby impeding homeostasis.
Alternatively, thermal coagulation is induced by exposure to a laser beam or an infrared light source. Though both sources have advantages over electrocoagulation, the infrared light sources are preferred because the light source is cheaper than and-YAG laser or other laser sources.
Known infrared light source thermal coagulation systems typically include a probe with a light radiation source enclosed in a housing. The source emits light radiation through a light exit surface for transmission along a light guide. The light guide is a light transmissive material which delivers the light radiation to the tissue surface and heats the surface. Examples of known apparatus for causing thermal coagulation using a light source are described in U.S. Pat. No. 4,233,493, issued Nov. 11, 1980, and U.S. Pat. No. 4,539,987, issued Sep. 10, 1985, the disclosures of which are incorporated herein by reference, and by Redfield Corporation Brochure Ĉ 1988 attached hereto as Appendix A.
In the known systems, however, the light guide is typically a straight rod or slightly bent and is thus often difficult to apply specific to the desired tissue region to be treated.
Further, the intensity of the emitted light cannot be precisely controlled and thus the coagulation is also not readily controlled. Another disadvantage is that the probe must be sterilized each time prior to its use.
It is therefore desirable to have an infrared coagulation device which overcomes the above-mentioned problems.
The present invention provides an infrared coagulation apparatus in which light is transmitted along a light guide having a bend that changes the direction of the light at a greater angle than in known systems, in which the intensity of the infrared light source is controlled by a feedback loop and which includes a disposable tip at the end of the light guide.
The infrared coagulation apparatus of this invention includes a non-coherent, multispectral light source having a spectral maximum of about 10,000 angstroms. A portion of the visible light spectrum is also emitted to ascertain operation of the lamp. The light emitted from the lamp is transmitted along a light guide which may be comprised entirely of quartz or which may include other light transmissive materials, such as sapphire, with a quartz portion located at the distal end. Advantageously, the distal end of the light guide includes a bend that causes the light to exit at angles up to an angle substantially perpendicular to the axis of the light guide and thus permits the probe to more easily contact the tissue area. A reflective coating surrounds the cylindrical walls of the light guide to further promote transmission of the light radiation along the path of the light guide as well as around the bend. A cladding layer, such as neoprene, surrounds the reflective coating to protect the coating, and an additional support cladding typically surrounds the neoprene cladding. A metal end cap is secured around the light guide near the distal end.
Alternatively, a straight quartz rod serves as the light guide and is covered with the reflective coating along the walls and at the distal end. A portion of the wall near the distal end is left uncoated so that the light reflects off the coating and exits at an angle substantially perpendicular to the axis of the rod.
Further, in accordance with this invention, a disposable contact tip covers the distal end of the light guide. The disposable tip includes a plastic cap that is secured onto the metal end cap and a Teflon or PVC plate optical window that covers the polished end surface of the light guide.
Alternatively, the disposable tip and sheath includes a plastic cylindrical body having a Teflon or PVC optical window which covers the contact end of the cylindrical body. A step-down section is attached to the opposite end of the cylindrical body and is arranged to be concentric with the cylindrical body but with a smaller diameter than the cylindrical body for secure insertion into the metal end cap of the light guide. A clear plastic sheath is also attached at this end of the cylindrical body and is sealed over the step-down section and extends over the surface of the cladding. The proximal end of the sheath is attached to a retainer ring having another step-down section which is capable of sliding over a retaining collar in the cladding to secure the proximal end of the sheath to the cladding. A pull tab is provided at the proximal ring so that the sheath and end cap can be removed after use by pulling on the pull tab and tearing a weakened notch in the step-down section to permit the sheath to be torn off the cladding and prevent its reuse.
In further accordance with the,invention, a power supply and control circuit controls the operation of the infrared lamp. A microcontroller delivers control signals to a triac which controls the current supplied by a step-down transformer to the infrared lamp. The microcontroller also receives a dwell time adjustment signal which controls the length of the pulses of the infrared lamp. The microcontroller also controls a lamp-on indicator LED and a digital read out lamp which indicates the length of the light pulses. Advantageously, a feedback circuit is also provided which includes a photo-diode that delivers a signal proportional to the intensity of the infrared lamp to an operational amplifier. The op-amp delivers the signal to an analog-to-digital converter which supplies a converted signal to the microcontroller which, in turn, controls the triac accordingly in response to the intensity detected.
The infrared coagulator apparatus of the invention causes thermal coagulation by elevating the tissue temperature to about 100xc2x0 C. without smoke or odor. The apparatus may be used for coagulation of bleeding, such as at the donor sites of hair transplant plugs. The coagulator is also suitable for causing coagulation at a hemorrhoidal plexus to cause the plexus to shrink and recede. Additionally, the coagulator may be used to remove decorative tattoos, reduce swollen nose membranes caused by chronic rhinitis, dry up genital warts or to remove warts or other skin lesions.
Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings.